Panels are typically installed over the ceilings and walls of rooms to provide an aesthetically pleasing appearance. Panel materials for such a finished appearance, e.g., wood or metal, do not typically improve room acoustics because the materials are substantially non-sound-absorbing. Such panels have been made more acoustically transparent or sound absorbing by providing holes through the panels, e.g., by providing edge-to-edge grooves on both faces of the panel, thus creating holes at the intersections of the grooves. Another method has been to bore holes through the panels or to bore holes on one face and provide edge-to-edge grooves on the opposite face. When such panels are installed, the back face of the panel is covered edge-to-edge by an expanse of an acoustically absorptive material.